Division By Zero
by Mauve Alert
Summary: Theta. The measure of an angle. A letter. A stupid little oval with a stupid little line through it. An outlandish nickname that nobody will ever call him again.


A/N - Luke and Sophie are companions from my fics _Denaturing_, _Brownian Motion_, and _Catalyst_ (if any regular readers can think up a name for this series, do tell) - but this little piece can pretty much stand on its own, I think.

And so I give you: the result of too little sleep and too much pre-calculus. Enjoy.

Typos edited 5/02/07.

* * *

**Division by Zero**

"Theta. . ."

The Doctor looks up sharply from his book, opens his mouth to demand how she knows that name.

". . . equals three pi over two," Sophie finishes, frowning at her notebook. "Right?" She is sprawled out on the floor in front of the hearth in a most undignified way, surrounded by textbooks, bits of paper, and numerous pencils with broken tips.

"Don't ask me," Luke replies, without taking his eyes off his own book. "I'm a biology guy, remember?"

Theta. The measure of an angle. A letter. A stupid little oval with a stupid little line through it.

An outlandish nickname that nobody will ever call him again.

It's funny, what odd things bring back the hurt after all these years. His hearts are pounding loud and fast in his ears and he feels the elaborate duct-tape repairs around them starting to peel. Control yourself, he tells himself sternly, and realizes that he sounds like a Time Lord. Self-control was always a Time Lord ideal; he hated them for it, found it. . . inhuman.

He's always been a little too human for his own good. Too human to be a Time Lord and too much Time Lord to be human, a balancing act he's never quite gotten right. It's confusing, sometimes, not knowing what he is.

He's settled for being the Doctor. It's enough, most of the time, because it has to be. He hasn't got anything else.

"I flunked Bio," sighs Sophie, tapping buttons on her calculator and scribbling down the results in a calculus frenzy. The Doctor can't understand why she's doing homework that she'll never pass in, studying for the degree she'll never receive, but doesn't mention it. Part of Sophie is still desperately trying to believe that "fifty megaton nuclear bomb" really is just another word for "banana," and that she still has a home to go back to.

"I thought you said you flunked English," the Doctor puts in, to escape both his thoughts and his new tendency to eavesdrop.

"I did," Sophie says, and sighs again.

Luke arches a brow at her. "Is this flunking as in, I only got a B instead of an A, or honest-to-God failing?"

Sophie considers. "Which would you despise me for more?"

"The first one, naturally."

The Doctor laughs with his companions. He's always loved humans a little too much for his own good. Humans are allowed to fail; they're allowed to laugh about failing. And the Doctor, who scored 51-percent on his second try, has always envied them that.

The sum of a human and a Time Lord is undefined. x/2 + x/2 equals x, but x/2 + y/2 cannot be simplified any further; unlike terms cannot be combined. He is an expression, not an equation, and only equations can be solved. No equals sign, no value, no solution.

He is an unknown quantity, unquantifiable, a number divided by zero. There is no name for what he is so he makes some up as he goes along, and some even stick, like Theta Sigma and the Doctor. Susan called him Grandfather and Ace called him Professor and sometimes Sophie calls him Daddy Dearest just to annoy him, but eventually they all fade away; Susan died and Ace left and there's no one left in the universe but him who remembers Theta Sigma. One day Sophie will be gone and Daddy Dearest will be, too, and one day the Doctor just won't be enough anymore when someone asks, "Who are you?"

Sophie places her notebook on his lap and gives him a pleading look. "Will you check these for me? Please?"

He raises a brow. "What makes you think I know calculus?"

"You're the Doctor," she says, as if this explains everything.

"Good answer," he replies, and picks up the notebook to look over her work.

For now, he's the Doctor, and it's enough because it has to be.

* * *


End file.
